1. Field of the Invention
The invention relates to dispensing materials from a container using apparatus including a follower plate which is lowered into the container housing the material to be dispensed. In particular, the invention relates to improved sealing means for use in preventing leakage of such material at the interface of the plate and the inner wall or surface of the container as the plate is being lowered into the container in a known manner.
2. Description of the Prior Art
The viscosity of materials to be dispensed using apparatus of the present invention varies depending upon the specific application, and it is not unusual to find materials which are not particularly viscous and are substantially free flowing. On the other hand in certain applications such materials may be extremely viscous and require the application of considerable heat and/or pressure in order to render such materials dispensable. The present invention is applicable to apparatus for dispensing highly viscous materials and also useful with substantially free flowing materials.
In one form of apparatus of the type contemplated by the present invention a plate is caused to reciprocate into and out of the open end of a drum-like container housing the material to be dispensed. Examples of such a plate are disclosed in Moore, U.S. Pat. Nos. 4,270,674 and 4,344, 547. In operation, as the plate enters the drum it engages the inside surface of the drum and the material therein. As the plate travels towards the closed base of the drum it causes the material sandwiched or pressured therebetween to be dispensed, as for example, by forcing the material through an opening in the plate. Such dispensing may be facilitated by means of a pump associated with such opening to pump the material therethrough as the plate is lowered into the drum. The dispensing operation may be further facilitated by applying heat to the material within the drum. This may be accomplished by, for example, utilizing a plate which includes a heating element affixed thereto or disposed internal thereof. In some instances the material may be so highly viscous as to require the combination of such heat, pressure and pumping action to adequately dispense the material. Examples of a dispensing apparatus which may rely upon heat, pressure and pumping is disclosed in Moore, U.S. Pat. Nos. 3,982,699 and 4,355,734.
As the plate is lowered into the drum and engages the material, there is a tendency for the material to flow from the bottom of the plate over the top of the plate at the peripheral surface or edge thereof where the plate is adjacent to the inside surface of the drum. For example, in those instances where the plate is cylindrical and is caused to extend into a cylindrical drum for purposes of dispensing material from within the drum, there is a tendency for the material to flow or leak between the outer periphery of the cylindrical plate and the inside surface of the drum. In order to prevent such leakage and to direct substantially all of the material through the dispensing opening in the plate, sealing means or wipers have been used. For example, the cylindrical plate discussed above may be encircled with one of more resilient sealing means which serve to scrape the inside surface of the drum and also to prevent or reduce leakage at the interface between the inside surface of the drum and the periphery of the plate. Such wipers generally are single piece, O-ring-like resilient seals, either solid or inflated, which are stretched over the end of the plate and caused to seat in an associated groove which extends about the peripheral surface of the plate. Examples of such wipers are disclosed in U.S. Pat. Nos. 3,282,469; 3,412,903; 3,637,111; 3,758,003; 3,976,229; 4,073,409; 4,227,069; 4,195,755; 4,240,567; 4,534,493; 4,592,491; 4,635,820; and, 4,661,688.
There are a number of problems associated with the use of such wipers. For example, optimally, the wiper should rotate or roll along the internal wall of the container during movement within the container. However, there is a tendency for such prior art wipers to twist apart and fall off of the plate during use due to the nature of the synthetic or other resilient materials used in making such sealing means, the configuration of the groove, and the configuration of the container from which material is being dispensed. In particular, there is a tendency for one portion of the wiper to become flattened and thereby prevented from rolling while the remaining portion of the wiper is free to roll. Such might occur, for example, in those instances where the container has been deformed or is otherwise bent out of shape. The result will be that the rolling portion of the wiper will twist off or sever from the flattened non-rolling portion and will fall out of the groove as the plate reciprocates relative to the container.
Other problems involve routine wear and tear, as well as unexpected damage which results from the abrasive environment, and often high temperatures, to which such wipers are subjected. For example, replacement of such wipers often requires stretching a new wiper over the end of a very hot plate, or waiting until such plate cools, both being undesirable alternatives. In addition, damage involves replacement of the entire wiper.
In U.S. Pat. No. 4,090,640, the use of a segmented metallic seal has been proposed to obtain a piston-like seal. However, such seals do not provide the desired rolling action, the individual metal segments being polygonal in cross-section and fastened to one another at adjacent ends by means of connecting pins.
As a result of the high temperatures encountered in some applications, there is a tendency for the wiper to expand and fall out of its associated groove. One means to prevent this from occurring involves the use of a seal retaining clip such as is disclosed in U.S. Pat. No. 4,632,281. This is an undesirable approach at least to the extent that additional hardware is required. Another means to prevent this problem from occurring involves the use of wipers which are stretched over the plate and into the groove, such wipers obviously being subjected to great tension. This is also undesirable in that if such a wiper is cut during use of otherwise, the wiper will vary rapidly tear to such an extent as to require replacement.
Accordingly, it is an object of this invention to provide apparatus for dispensing material using a follower plate having a resilient sealing means which does not twist apart and fall off of the plate during use.
Another object of this invention is to provide apparatus for dispensing material from a container using a follower plate having a resilient sealing means which rolls upon the inside wall of the container during use and wherein any undesirable prevention from rolling of a portion of such sealing means will not affect the rolling motion of any other portion such sealing means.
Still another object of this invention is to provide apparatus for dispensing material from a container using a follower plate having resilient sealing means which can be readily replaced whether the plate is cold or hot without stretching or otherwise tensioning the sealing means during installation or use.
A further object of this invention is to provide apparatus for dispensing material from a container using a follower plate having resilient sealing means which does not require total replacement when only a portion is in need of repair.
Still of further object of this invention is to provide apparatus for dispensing material from a container using a follower plate having resilient sealing means with abutting ends which do not need to be fastened to one another.
Yet another object of this invention is to provide apparatus for dispensing material from a container using a follower plate having resilient sealing means which does not require separate hardware such as a retaining clip to hold the sealing means in its associated groove.